If you are wondering how a simple IC 555 can be used for making a powerful voltage doubler circuit, then this article will help you to understand the details and construct the design at home.

What's a Voltage Doubler

If you are new to voltage doubler concept and desire to learn the concept in-depth, we have a good elaborate article in this website explaining different voltage multiplier circuits for your reference.

Briefly, a voltage multiplier works by using only diodes and capacitors and the network may be capable of raising a small voltage input into a significantly high voltage output.

Voltage multiplier concept was first discovered and used practically by British and Irish physicists John Douglas Cockcroft and Ernest Thomas Sinton Walton, hence it is also called the Cockcroft–Walton (CW) generator.

A voltage doubler circuit is also a form of voltage multiplier where the diode/capacitor stage is restricted to a couple of stages only, so that the output is allowed to produce a voltage that may be twice of the supply voltage.

Since all voltage multiplier circuits mandatorily require an AC input or a pulsating input, an oscillator circuit becomes essential for accomplishing the results.

IC 555 Pinout Details

Circuit Schematic of Voltage Doubler using IC 555

Referring to the above example, we can see an IC 555 circuit configured as an astable multivibrator stage, which is actually a form of oscillator, and is designed to produce a pulsating DC (ON/OFF) at its output pin#3.

If you recall, we had discussed an LED torch circuit in this website, which quite identically uses a voltage doubler circuit, albeit the oscillator section is created using an IC 4049 gates.

Basically, you can replace the IC 555 stage with any other oscillator circuit and still get the voltage doubling effect.

However using IC 555 has a slight benefit since this IC is able to generate more current than any other IC based oscillator circuit without using any external current amplifier stage.

How the Voltage Doubler Stage Operates

As can be seen in the above diagram, the actual voltage multiplication is implemented by the D1, D2, C2, C3 stage, which are configured as a half-bridge 2-stage voltage multiplier network.

Simulating this stage in response to the IC 555's pin#3 situation can be a little difficult, and I am still struggling to get it running in my brain correctly.

As per my mind simulation, the working of the mentioned voltage doubler stage can be explained as given in the following points:

When the IC output pin#3 is in its low logic or ground level, D1 is able to charge C2, since it is able to get forward biased through C2 and pin#3's negative potential, also simultaneously C3 is charged via D1, and D2.

Now, in the next instant as soon as pin#3 becomes at high logic or at the positive supply potential, things get slightly confusing.

Here C2 is unable to discharge via D1, so we have a supply level output from D1, from C2, and from C3 also.

Many of the other online sites say that at this point the stored voltage inside C2, and the positive from D1 is supposed to combine with the output of C3 to produce a doubled voltage, however that does not make sense.

Because, when voltages combine in parallel, the net voltage does not increase. The voltages must combine in series to cause the desired boosting or the doubling effect.

The only logical explanation that can be derived is, when pin#3 becomes high, C2's negative being at the positive level and its positive end also held at the supply level, it is forced to produce a reverse charge pulse which adds up with the C3 charge, causing a instantaneous potential spike having a peak voltage twice that of the supply level.

If you have a better or technically more correctexplanation, please do feel fre to explain it through your comments.

How much Current can an IC 555 voltage doubler able to Supply?

Pin#3 of the IC is assigned to deliver a maximum of 200mA current, therefore the maximum peak current can be expected to be at this 200mA level, however the peaks will get narrower depending on the C2, C3 values. Higher value capacitors might enable fuller current transfer across the output, therefore make sure the C2, C3 values are optimally selected, around 100uF/25V will be just enough

A Practical Application Circuit of a Voltage Doubler Circuit

Although a voltage doubler circuit can be useful for many electronic circuit applications, a hobby based application could be to illuminate a high voltage LED from a low voltage source, as shown below:

In the above circuit diagram we can see how a IC 555 based voltage doubler is used for illuminating a 9V LED bulb from a 5V supply source, which would normally be impossible if the 5V was directly applied on the LED.

Relation between Frequency, PWM and the Voltage Output Level

The frequency in any voltage doubler circuit is not crucial, however faster frequency will help you to get better results than slower frequencies.

Similarly for the PWM range, the duty cycle should be roughly 50%, narrower pulses will cause lower current at the output, whereas too wide pulses will not allow the relevant capacitors to discharge optimally, again resulting in an ineffective output power.

In the discussed IC 555 astable circuit, the R1 can be anywhere between 10K and 100K, this resistor along with the C1 decides the frequency. C1 consequently can be anywhere between 50nF to 0.5uF.

R2 will fundamentally enable you to control the PWM, therefore this can be made into a variable resistor through a 100K pot.

If you have any doubts or something more interesting regarding this IC 555 based voltage doubler circuit, please do share it through your valuable comments.

In this project we are going to run a unipolar stepper motor using 555 timer. Apart from 555 timer we also need IC CD 4017 which is a decade counter IC.

By Ankit Negi

Any unipolar motor can be connected to this circuit for performing specific task, though you need to do some small changes first.

Speed of the stepper motor can be controlled from a potentiometer connected between discharge and threshold pin of 555 timer.

Some basics of stepper motor:

Stepper motors are used in such areas where specific amount of rotation is required as d.c motor cannot start and stops instantly at the required position. Like in a 3D PRINTER. There are two types of stepper motor: UNIPOLAR and BIPOLAR.

As the name suggests unipolar stepper motor contains windings with common wire which can be easily energized one by one.

Whereas bipolar stepper motor does not have a common lead between coils due to which it cannot be drive simply by using this circuit. To drive bipolar stepper motor we need an h-bridge circuit.

COMPONENTS:

1. 555 TIMER IC

2. CD 4017 IC

3. RESISTORS 4.7K, 1K

4. POTENTIOMETER 220K

5. 1 uf CAPACITOR

6. 4 DIODES 1N4007

7. 4 TRANSISTORS 2N222

8. UNIPOLAR STEPPER MOTOR

9. DC POWER SOURCE

PURPOSE OF 555 TIMER:

555 timer is required here to generate clock pulses of particular frequency (can be varied using 220k pot) which determines the speed of the stepper motor.

IC 555 Pinout details

PURPOSE OF CD4017:

As already mentioned above, it is a decade counter IC i.e., it can count up to 10 clock pulses. What make this IC special is that it has its own inbuilt decoder. Due to which you do not have to add an additional IC to decode binary numbers.

4017 counts up to 10 clock pulses from 555 timer and gives high output corresponding to each clock pulse one by one from its 10 output pins. At a time only one pin is high.

PURPOSE OF TRANSISTORS:

There are two purposes of transistor here:

1. Transistors act like switches here, thus energizing one coil at a time.

2. Transistors enable high current to pass through them and then motor, thus excluding 555 timer completely as it can supply very little amount of current.

CIRCUIT DIAGRAM:

Make connections as shown in figure.

1. Connect pin 3 or output pin of 555 timer to pin 14 (clock pin ) of IC 4017.
2. Connect enable pin or 13th pin of 4017 to ground.
3. Connect pins 3,2,4,7 one by one to transistors 1,2,3,4 respectively.
4. Connect 10 and 15th pin to ground through a 1k resistor.
5. Connect common wire of stepper motor to the positive of supply.
6. Connect other wires of stepper motor in such a way so that coils are energized one by one to complete one full revolution properly.( you can look into datasheet of the motor provided by the manufacturer)

WHY OUTPUT PIN 10 OF IC 4017 IS CONNECTED TO ITS PIN 15 (RESET PIN)?

As already mentioned above 4017 counts clock pulses one by one up to 10th clock pulse and gives high output on output pins accordingly, each output pin goes high.

This causes certain delay in rotation of motor which is unnecessary. As we require only first four pins for one complete revolution of motor or first four decimal counts from o to 3, pin no. 10 is connected to pin15 so that after 4th count IC resets and counting starts from the beginning again. This ensures no delay in motor’s rotation.

WORKING:

After making connections properly if you switch on the circuit motor will start rotating in steps. 555 timer produces clock pulses depending on the values of resistor, potentiometer and capacitor.

If you change value of any of these three component frequency of clock pulse will change.

These clock pulses are given to IC CD 4017 which then counts the clock pulses one by one and give 1 as output to pin no 3,2,4,7 respectively and repeats this process continuously.

Since transistor Q1 is connected to pin 3, it switches on first then transistor Q2 followed by Q3 and Q4. But when one transistor is on all other remain off.

When Q1 is on it acts like a closed switch and current flows through common wire to wire 1 and then to ground through transistor Q1.

This energizes coil 1 and motor rotates at some angle which depends on clock frequency. Then same thing happens with Q2 which energizes coil 2 followed by coil 3 and coil 4. Thus one complete revolution is obtained.

When potentiometer is rotated:

Let’s say initially position of pot is such that there is maximum resistance (220k) between discharge and threshold pin. Formula for frequency of output clock pulse is :

F = 1.44/(R1 + 2R2)C1

It is clear from the formula that frequency of clock pulses decreases as value of R2 increases. Thus when R2 or pot’s value is maximum, frequency is minimum due to which IC 4017 counts more slowly and gives more delayed output.

Using IC 555 for the Inverter

The diagram above shows the entire design of the proposed SPWM inverter circuit using IC 555, where the center IC 555 and the associated BJT/mosfet stages forms a basic square wave inverter circuit.

Our aim is to chop these 50Hz square waves into the required SPWM waveform using an opamp based circuit.

Therefore we accordingly configure a simple opamp comparator stage using the IC 741, as shown in the lower section of the diagram.

As already discussed in our past SPWM article, this opamp needs a couple of triangle wave sources across its two inputs in the form of a fast triangle wave on its pin#3 (non-inverting input) and a much slower triangle wave at its pin#2 (inverting input).

IC 555 Pinouts

Using IC 741 for the SPWM

We achieve the above by using another IC 555 astable circuit which can be witnessed at the extreme left of the diagram, and use it for creating the required fast triangle waves, which is then applied to the pin#3 of the IC 741.

For the slow triangle waves we simple extract the same from the center IC 555 which is set at 50% duty cycle and its timing capacitor C is tweaked appropriately for getting a 50Hz frequency on its pin#3.

Deriving the slow triangle waves from the 50Hz/50% source ensures that the chopping of the SPWMs across the buffer BJTs is perfectly synchronized with the mosfet conduct ions, and this in turn ensures that the each of the square waves are perfectly "carved" as per the generated SPWM from the opamp output.

The above description clearly explains how to make a simple SPWM inverter circuit using IC 555 and IC 741, if you have any related queries please feel free to use the below given comment box for prompt replies.

Update:

A deeper investigation reveals that the slow triangle waves must have a frequency of 100Hz and not 50 Hz for creating correctly dimensioned SPWMs, this may be done by using a frequency doubler stage bewtween pin#2 of the IC 741 and the 50Hz from pin#6/2 of the center 555 IC.

In this project we are going to learn the basic specifications of a servo motor and also how to operate a Servo Motor using a 555 timer IC, and a couple of push buttons.

By Ankit Negi

WHY SERVO?

Servo Motors are used in variety of fields. These are mainly used as actuators in those areas where we need a precise movement to control output load.

Best example is a RC car. Let's see you want movement of 45 degree, not more not less. In that case you can't use a simple DC motor because it will overshoot the desired position every time you power it up.

And thus we need a Servo Motor to achieve this task as it will not only make a precise 45 degree rotation but will also stop smoothly at the desired position.

FEW TECHNICAL POINTS ONE MUST KNOW:

A) Before buying or using a servo one must know what's inside it and how it works. a servo motor is made up of three key components:

To rotate the motor clockwise, on time period of clock pulse must be greater than 1.5 milliseconds and to rotate it anticlockwise on time period must be less than 1.25 milliseconds but frequency should lie between 50 to 60 Hertz.

And thus we are going to use a 555 timer to generate such clock pulses for us.

CIRCUIT DIAGRAM SHOWING HOW TO RUN A SERVO MOTOR USING IC 555:

Connect positive and negative pin of motor to positive and negative terminal of the battery respectively. And connect signal or reference pin to the collector terminal of the transistor.

CIRCUIT WORKING:

1. When forward push button is pressed-

When this case arises then 68 K resistor get connected between discharge and threshold pin. Now initially capacitor is not charged so pin 2 is at 0 volt which is less than 1 by 3 of applied voltage.

This resets the flip flop inside the 555 and gives logic 1 at the output terminal at which base of the transistor is connected.

This causes transistor to turn on and conduct current directly to ground due to which signal pin of motor get zero volt as this pin is directly connected to Collector terminal.

Since capacitor start charging when output is 1, the output becomes 0 as soon as voltage across capacitor becomes greater than 2 by 3 of applied voltage as it is directly connected to threshold pin.

Now transistor will be off and signal pin will get logic 1.

In this way pwm signals are generated at the reference pin of motor. Now in this case on time period of generated pulse is greater than 1.5 milliseconds, which you can calculate by the duty cycle formula for 555. And thus we get 90 degree clockwise rotation of motor as explained in above paragraph.

1. When backward push button is pressed-

When this case arises then 10 K resistor get connected between discharge and threshold pin which is less than 68k ohm resistor. Thus in this case the on time period of pulse is lesson than 1.5 milliseconds, which you can calculate by the duty cycle formula for 555.

Now the pwm is generated at the reference pin of motor the same way as in the above case. And thus we get 90 degree anticlockwise rotation of motor as explained in above paragraph.

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Swagatam is an ardent electronic researcher, inventor, schematic/PCB designer, manufacturer, and an avid publisher. He is the founder of https://www.homemade-circuits.com/where visitors get the opportunity to read many of his innovative electronic circuit ideas, and also solve crucial circuit related problems through comment discussion.